Referring, for example, to the fuel gas supply adjusters (also referred to as flame length adjusters or flame adjusters) for gas lighters, there are known techniques as disclosed, for example, in Japanese Utility Model Publication No. 866/1972, Japanese Unexamined Utility Model Publication No. 154874/1979, Japanese Utility Model Publication No. 5562/1987 and Japanese Patent Publication No. 52770/1990.
As will be appreciated by reading these official gazettes, the mechanisms of controlling the gas supply can roughly be grouped into two types. The first one is of compression adjustment type, in which a porous elastic filter is compressed for flow rate adjustment (Japanese Unexamined Utility Model Publication No. 154874/1979 and Japanese Utility Model Publication No. 5562/1987); and the second one is of an area adjustment type, in which the gas permeating area of a noncompressible filter is changed for flow rate adjustment (Japanese Utility Model Publication No. 866/1972 and Japanese Patent Publication No. 52770/1990).
While the compression adjustment type flow rate adjuster is still now utilized frequently in the commercially available products, it suffers a problem in the stability of adjustment, as described in Japanese Utility Model Publication No. 866/1972 and Japanese Unexamined Utility Model Publication No. 154874/1979, due to the instability of the elastic filter employed therein which increases with time.
Meanwhile, the area adjustment type flow rate adjuster is free from such problem of increasing instability with time because adjustment can be achieved without affecting the filter itself, and thus the area adjustment type is theoretically expected to have superior adjusting function to the compression adjustment type.
However, the technique of Japanese Utility Model Publication No. 866/1972 has not yet been realized in actual products, although it has passed a considerable time since the technique was disclosed. It was proved by experiments using trial products fabricating according to the constitution as disclosed in Japanese Utility Model Publication No. 866/1972 that the gas flow rate is abnormally increased at the initial ignition after a predetermined time of interval to cause ignition failure, formation of abnormally long flame, flickering of the flame, poor adjustability and many other problems, and thus the theoretically expected adjusting function can not always sufficiently be exhibited.
Meanwhile, the technique disclosed in Japanese Patent Publication No. 52770/1990 can fully exhibit the merit of the area adjusting system and is realized in the commercially available products practically utilized. However, this technique merely enables automatic adjustment of the flame length (flame height) within a predetermined range and no consideration is given as for enabling free adjustment of the flame length as a user desires.
In view of the problems inherent in the prior art, the present inventor made extensive studies with a view to providing a supply adjuster which enables free adjustment of the flame length and can exhibit a stable adjusting function as can be expected in the area adjustment type flow rate adjuster. They made various experiments from different angles particularly on the technique of Japanese Utility Model Publication No. 866/1972 so as to analyze the causes of the problems mentioned above to assure themselves of the facts that the causes reside in the thickness of the filter, the relationship between the filter and the elastic body, and the relationship between the peripheral members for mounting or housing them.
The present inventor consequently came to know that free adjustment of the flame length becomes possible and that the stable adjusting function as can be expected in the area adjustment type flow rate adjuster can fully be exhibited by using a membrane filter which can provide a minimum necessary fuel retaining volume as the filter so as not to feed an excessive amount of fuel at the initial ignition and by incorporating the membrane filter in a fully shielded structure with a minimum necessary space being secured therein.